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(11) | EP 2 658 061 A3 |
| (12) | EUROPEAN PATENT APPLICATION |
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| (54) | Communication line isolator |
| (57) An isolator 10 is formed with an isolation transformer 13 that blocks an abnormal
voltage entering from a communication line 30 and protects a protection target device
40. A pulse transformer 43 in the device 40 includes a primary winding 43a connected
to a secondary winding 13b of the transformer 13 and a secondary winding 43b connected
to an inner circuit. A medium tap of the primary winding 43a is grounded through an
inner capacitance Ci of the device 40. A parasitic capacitance Cs between the primary
winding 13a and the secondary winding 13b of the transformer 13 and the inner capacitance
Ci are connected in series, an abnormal voltage is divided by the capacitance Cs and
the capacitance Ci, and a capacitance value of the capacitance Cs is set such that
the divided voltage of the capacitance Ci is equal to or below a predetermined value.
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